Service providers and device manufacturers (e.g., wireless, cellular, etc.) are continually challenged to deliver value and convenience to consumers by, for example, providing compelling network services. IEEE 802.11 (e.g., the IEEE 802.11 standard, IEEE std. 802.11-2012, published Mar. 29, 2012) is a set of standards for implementing wireless local area network communication in various frequency bands (e.g. WiFi). The 802.11 standard comprises a series of modulation techniques that use a same basic protocol, but is broken up into a family of bandwidths having various transmission rates. For example, in .11a/g, 20 MHz channel widths are defined, in .11n 40 MHz channel widths are defined, and in .11 ac both 80 and 160 MHz.
The evolution of WiFi has historically been to increase data rate. But, the newly developed .11ah actually targets comparatively lower rate services. In 802.11 ah, a very low data rate operation is being enabled. In .11 ah, the bandwidths defined are 1 MHz, and a set of down-clocked .11ac bandwidths, namely 2, 4, 8 and 16 MHz, where the down clocking is 10x are also defined. The 1 MHz rate is not derived from the .11n/ac rates, and thus this bandwidth mode is designed more or less independently. For its independent development, a 1 MHz system is likely to use a 32 point Fast Fourier Transform (FFT), as opposed to the minimum of 64 called for in .11 ac.
Data packets corresponding to frequency bands are typically transmitted having a preamble portion. With the adoption of a 1 MHz bandwidth having a 32 point FFT, a new preamble structure needs to be designed. In developing the preamble, one of the main considerations is coexistence and detection of the other bandwidths of operation, for example with the 2, 4, 8 and 16 MHz bands discussed above. In a transmission, any of those bandwidths are possible and a receiver needs a mechanism in order to determine the type of packet during the preamble portion of the packet.